Research On Mechanism Of Insulation Fault Caused By Amorphous Alloy Transformer Debris

The core of amorphous alloy transformer is manufactured by amorphous strip that significantly reduces load loss in distribution network,but the power supply reliability of distribution network is critically influenced by the insulation fault which is caused by the motion and settlement of amorphous alloy debris.Therefore,this paper studies generation mechanism of amorphous debris and the way that amorphous debris influences the insulation performance.This paper simulates the various working condition by applying different load current and calculates the deformation of amorphous alloy core,the results demonstrates that:When the load current is rated current,the probability of fragmentation is not large;However,when the load factor is 1.2,the deformation of the amorphous core is up to 150 micron,which exceeds the limit of the fracture of the material at 70 micron;especially,when the short circuit fault occurs,the deformation of the core caused by the vibration of the winding and the amorphous core is up to 520 micron.The flow and temperature field of amorphous alloy transformer is calculated based on the finite volume method.The temperature rise of the high and low voltage winding of amorphous alloy transformer is 52K and 60K respectively under the full load condition and the correctness of the result is proved by the comparison with the empirical formula;the flow law is analyzed further,the insulation oil flow rate reached 0.028m/s in the high and low voltage winding,while the maximum flow rate at the upper part of the winding is 0.035m/s,and the flow rate in the case of changes in load coefficient is not changed.Debris of different sizes are divided into two categories according to flow rate,one is the small amorphous debris moving with insulating oil;for such debris,this paper presents the sub model of amorphous alloy transformer and the fluid field of insulating oil in this model is consistent with the transformer.The path of debris is calculated in the sub model.Based on the path the discharge mechanism and condition caused by small debris are studied.Insulation degradation caused by debris is divided into three processes:micro discharge,corona discharge and breakdown discharge The generating conditions are obtained by using empirical formula,the result that the smaller the debris equivalent diameter,the more frequent the collision between the debris and the high and low voltage windings which is likely to cause discharge are obtained according to the discharge models,.Another type of debris will be settled in the insulating oil due to large gravity,Simulation results show that electric field distortion caused by same debris with different angle between windings are quite different;the larger the size of the debris or the greater the number will strength the greater distortion of the electric field.The magnitude of the electric field distortion caused by debris contact with the high and low voltage windings is greater than when not in contact.The conclusion that large size debris reduces the distance of the main insulation structure is obtained based on the research.The research content of this paper expatiates the mechanism of the insulation deterioration caused by the debris produced by the core during the operation of the amorphous alloy transformer,which can provide some theoretical basis and technical support for the design of the amorphous alloy transformer and the elimination of the insulation fault caused by the debris.